1. Field of the Invention
The present invention relates generally to devices and methods for selectively stimulating parts of the body, and more particularly to devices and method for selectively stimulating various nerves or selectively applying electrical stimulation to various other body parts.
2. Background Discussion
Women account for more than 11 million incontinence cases. One type of incontinence is stress urinary incontinence (SUI), where women experience involuntary loss of urine during normal daily activities and movements, such as laughing, coughing, sneezing and regular exercise. SUI may be caused by a functional defect of the tissue or ligaments connecting the vaginal wall with the pelvic muscles and pubic bone. Common causes include repetitive straining of the pelvic muscles, childbirth, loss of pelvic muscle tone, and estrogen loss. Such a defect results in an improperly functioning urethra. Unlike other types of incontinence, SUI is not a problem of the bladder.
Where stress incontinence is typically a result of an anatomical defect, another form of incontinence, urge incontinence, appears to be neurologically based and generally revealed as detrusor muscle instability or “bladder spasms.” As such it is usually not conducive to surgical correction. Urge incontinence may or may not result in urine leakage, but both conditions otherwise have similar symptoms and similar forms of treatment, which generally include a combination of behavioral modification (learned strategies for reducing the urge sensation, scheduled voiding, avoidance of bladder-stimulating substances such as caffeine, and pelvic muscle exercises, with or without biofeedback) and drug therapy (typically anticholinergeic agents such as oxybutynin or tolterodine). These treatments require life-long therapy. Unfortunately, behavioral modification requires continuous effort to maintain results and the available drugs have significant side effects for many patients causing 80% to discontinue therapy within a year. The alternative therapy is to modify lifestyle to accommodate the condition—frequent urination to avoid “accidents” and wearing protective pads or undergarments, depending on the severity of the condition.
Another approach for treatment is stimulation of the sacral and/or pudendal nerve. The sacral spinal nerve roots separate in pairs to exit laterally through the nerve root foramina. The main destinations for these roots are the sacral plexus. Nerves from this plexus provide the motor and sensory innervation of the lower limbs and pelvic organs. Specifically, the sacral plexus splits into five sacral nerve pair, sacral spinal nerves S1 to S5. These nerves supply the thighs and lower parts of the legs, the feet, most of the external genital organs, and the area around the anus. The pudendal nerve is the largest branch of the pudendal plexus and is composed of somatosensory, somatomotor and autonomic elements derived from the anterior primary divisions of the second, third and fourth sacral nerves. The pudendal nerve affects the function of the bladder, urethral sphincter and genitals. Lower branches of the pudendal nerve contribute to peristalsis of the colon and anal sphincter contraction force. The pudendal nerve is closer to the bladder, and its stimulation innervates the bladder, thus eliminating or lessening its contractions. At least one known commercial device stimulates the sacral nerve through a needle extended into the sacral nerve bundle. This device, however, supplies a continuous signal to provide constant stimulation of the nerve. Various drawbacks of this device include its invasive nature, and unwanted stimulation effects on other areas of the body, since the sacral nerve as a whole is being stimulated and multiple other areas of the body are innervated by such stimulation (i.e., resulting in leg twitches or the like).
A company called Advanced Bionics has an implantable stimulation device that targets the pudendal nerve specifically rather than the sacral nerve. This device is implanted in the vicinity of the pudendal nerve, but also is invasive and supplies a constant signal as described above and therefore, has the same drawbacks.
In addition to incontinence, women can suffer from other diseases as well, often simultaneously with incontinence. Interstitial cystitis is a chronic bladder condition involving an inflamed or irritated bladder wall. Patients with this condition may experience mild discomfort, pressure, tenderness, or intense pain in the bladder and surrounding pelvic area. Other symptoms may include an urgent need to urinate (urgency), frequent need to urinate (frequency), or a combination of these symptoms. The inflammation can lead to scarring and stiffening of the bladder, less bladder capacity (the bladder is able to hold less urine), and pinpoint bleeding in the bladder lining. In rare cases, ulcers form in the bladder lining. Of the more than 700,000 Americans estimated to have interstitial cystitis, about 90 percent are women.
Treatments for interstitial cystitis include oral medicines, such as aspirin, ibuprofen, other painkillers, antidepressants and antihistamines. Another treatment is bladder instillation (a bladder wash or bath) in which the bladder is filled with a solution that is held for varying periods of time before being emptied. These treatments require life-long therapy. Sacral nerve stimulation implants are also used for the treatment of interstitial cystitis, but, as stated previously, its invasive nature and unwanted stimulation effects on other areas of the body make this treatment undesirable. Surgery, considered a treatment of last resort, does not necessarily improve symptoms.
Other diseases that may occur simultaneously with urinary incontinence include fecal and anal incontinence. Fecal incontinence is the inability to control the bowels, and can have several causes with constipation being the most common. Fecal incontinence can also be caused by injury to one or both of the ring-like muscles at the end of the rectum called the anal internal and/or external sphincters. In women, the damage often happens when giving birth. Hemorrhoid surgery can damage the sphincters as well. Fecal incontinence can also be caused by damage to the nerves that control the anal sphincters or to the nerves that sense stool in the rectum. Nerve damage can also be caused by childbirth, a long-term habit of straining to pass stool, stroke, and diseases that affect the nerves, such as diabetes and multiple sclerosis. In addition, rectal surgery, radiation treatment, and inflammatory bowel disease can cause scarring that makes the walls of the rectum stiff and less elastic. Abnormalities of the pelvic floor, which is typically caused by childbirth, can also lead to fecal incontinence. Examples of some abnormalities are decreased perception of rectal sensation, decreased anal canal pressures, decreased squeeze pressure of the anal canal, impaired anal sensation, a dropping down of the rectum (rectal prolapse), protrusion of the rectum through the vagina (rectocele), and/or generalized weakness and sagging of the pelvic floor. Treatment depends on the cause and severity of fecal incontinence, and may include dietary changes, medication, bowel training, or surgery. A last resort is a colostomy, which is the surgical creation of an opening between the large intestine and the abdominal wall. More than one treatment may be necessary for successful control since continence is a complicated chain of events.
One type of treatment typically cannot be used to treat the different conditions described above, and, as indicated above, many of the known treatments are invasive or have other negative side effects. Accordingly, what is needed is an improved device and method for simultaneously treating different diseases or conditions.